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West Pacific/2015/09W/Archive/15
Public advisory TROPICAL STORM CHAN-HOM PUBLIC ADVISORY NUMBER 15 WIKI-HURRICANES FORECASTING CENTER 12:00 AM JST SAT JUL 04 2015 ...CHAN-HOM REMAINING HIGHLY DISORGANIZED... SUMMARY OF 12:00 AM JST...15:00 UTC...INFORMATION ------------------------------------------------------------------- LOCATION...11.4N, 148.8E CENTER POSITION CONFIDENCE: HIGH ... ± 20 MI... 30 KM ABOUT 305 MI...495 KM SE OF HAGATNA, GUAM MAXIMUM SUSTAINED WINDS...45 KT...50 MPH...80 KM/H MINIMUM BAROMETRIC PRESSURE...999 MB...29.50 INCHES PRESENT MOVEMENT...NNE AT 5 KT...6 MPH...9 KM/H DISCUSSION AND 48-HOUR OUTLOOK --------------------------------------------- At 12:00 am JST, the center of Tropical Storm Chan-Hom was situated near 11.4N, 148.8E, or about 305 miles (495 kilometers) southeast of Hagatna, Guam. Maximum sustained winds were 45 knots (50 mph, 80 km/h), with higher gusts. The minimum barometric pressure was 999 millibars (hPa; 29.50 inHg), and the cyclone was tracking north-northeast 5 knots (6 mph, 9 km/h). Due to the storm's currently ragged appearance, Chan-hom is expected to intensify at a slow pace, but the forecast track remains the same and puts the Mariana Islands under the gun for a tropical cyclone. NEXT ADVISORY ------------------- Next complete advisory at 06:00 am JST. $$ Forecaster TheAustinMan Discussion TROPICAL STORM CHAN-HOM PUBLIC DISCUSSION NUMBER 15 WIKI-HURRICANES FORECASTING CENTER 12:00 AM JST SAT JUL 04 2015 Over the past day, Chan-hom's organization has degraded enormously, and there is no evidence of the intensifying central dense overcast or developing eye it possessed just 24 hours ago. In the last six hours, some convection has initiated near the center of circulation, but the low-level vortex is still exposed and is visible on infrared imagery. Infrared and microwave imagery reveals that there are only isolated splotches of deep convections strewn about the low level cloud bands. Satellite intensity estimates have dropped and suggest that Chan-hom may be a minimal tropical storm or tropical depression. However, a 0748z Windsat scatterometer pass that despite Chan-hom's disheveled appearance, the storm still posseses a marked field of tropical storm-force winds in the southwestern quadrant and areas of 40 knot winds; one area of 50 knot winds was detected but was marked as suspect. Given this analysis, Chan-hom's intensity has been left at 45 knots with a pressure of 999 millibars. Present motion for Chan-hom has been set at 25/6, and it appears that Chan-hom is slowly making its northward turn and should eventually begin curving northwestward in the direction of the Mariana Islands. Chan-hom is largely being driven by a weakness in the ridge induced by a passing trough, which should eventually take the storm in the diretion of southern Japan or the East China Sea. Models have come into much better agreement as to what Chan-hom's track will be in the short-term, and have also shifted northwards. However, models diverge in the long-term concerning the trough's impacts on Chan-hom's motion. The 0z ECMWF brings Chan-hom into Okinawa and into China, while the 6z GFS and 0z CMC depict a recurve that takes Chan-hom into the Tokyo metropolitan area. The model spread indicates that Chan-hom could make landfall anywhere from Shanghai to Busan to Tokyo, and until better model consensus establishes itself, Chan-hom's track remains difficult to forecast in the long term. In the short term, the WHFC track follows the model consensus, while in the long-term the track is slightly weighted towards the GFS/CMC solution. The intensity forecast for Chan-hom remains generally the same as the last advisory. Given the disorganized and sheared structure the tropical cyclone currently posseses, any intensification in the short-term will likely be slow, but rapid reorganization is possible. Currently wind shear is in the 10-20 knot range, which while less than yesterday should slow strengthening if it continues to persist. However, wind shear values have been dropping quite copiously over the past 24 hours, and a swath of area surrounding the Mariana Islands and areas north of where Chan-hom is currently has extremely low wind shear as analyzed by CIMSS. In addition, convection appears to be letting up in association with the convective system that was producing unfavorable upper-level winds yesterday. Chan-hom has the ability to take advantage of these conditions, but until it develops the inner core expressed verbosely in the last advisory, Chan-hom will find difficulty in steadily strengthening. With this advisory, the WHFC anticipates slow strengthening throughout today that gradually accelerates as Chan-hom nears the Mariana Islands. After the storm passes the Mariana Islands, Chan-hom is expected to take off and potentially become a highly powerful typhoon. INIT 03/1500Z 11.4N 148.8E 45 KT 50 MPH 12H 04/0000Z 12.3N 148.7E 45 KT 50 MPH 24H 04/1200Z 13.2N 148.1E 50 KT 60 MPH 36H 05/0000Z 12.2N 146.9E 65 KT 75 MPH ... APPROACHING MARIANA ISLANDS 48H 05/1200Z 15.5N 144.9E 75 KT 85 MPH ... PASSING MARIANA ISLANDS 72H 06/1200Z 17.9N 141.0E 105 KT 120 MPH 96H 07/1200Z 22.5N 136.5E 135 KT 155 MPH 120H 08/1200Z 27.7N 133.0E 120 KT 140 MPH $$ Forecaster TheAustinMan